New methods for easy, rapid enzymatic assays in very small sample volumes (sub-microliter) will greatly benefit the prognosis, diagnosis and detection of cancer. The goal of Phase I is to demonstrate the feasibility of adapting silicon microsampling and assay devices originally developed for blood glucose monitoring, to enzyme activity measurement using a novel technique, "Diffusive Enzyme Activity Measurement." An electrochemical redox-mediated prostatic acid phosphatase (PAP) assay will be the example, requiring no on-chip biologicals (providing a potentially long shelf-life). Silicon microchips with the novel diffusional microfluidics will be designed and fabricated. A computer simulation model will be used in the development of the assay. The enzyme chosen for Phase I is a known cancer marker for prostate cancer. Potential commercial applications include enzyme activity measurements on sub-microliter liquid samples, such as blood drawn from experimental animals (or humans), tissue extract specimens, purified enzymes and drug discovery research and development.